The present invention concerns a fluid pressure actuated expansion device for a mandrel equipped with such expansion devices designed for holding in place spools or reels of material in the form of sheets or the like, such spools being made with cores of cardboard, steel aluminum or any other material, or simply consisting of material wound around itself and an expansion shaft with such devices.
Currently, there are commercially available several known types of pressure fluid actuated expansible mandrels securing spools of cardboard, plastic material, fabric or the like, all of which are essentially based on the principle of obtaining the expansion of longitudinal elements or pins so as to protrude from the bearing surface of the shaft and allow easy sliding on and off the shaft of spools with or without core, and securing the spools in place by expansion of said elements, which may operate locally or along a shaft generatrix.
The above mentioned mandrels are essentially of two types:
In the first type, the mandrel consists of a tube into which is fitted a bladder made of elastic material; when expanded, this bladder actuates lognitudinal elements or pins, causing them to protrude from the surface of the shaft. This arrangement accomplishes the purpose of locking the spool core in place; however, it has drawbacks due to the fact that since the bladder is located inside the shaft its replacement, in case of failure, requires removal of the shaft journals and disassembly of the expanding elements, an operation which is rather time-consuming.
In other types of mandrels, one or several elastic bladders are fitted into T or dovetail splines machined on the shaft surface; this makes replacement of a bladder somewhat easier than in the preceding type of shaft, but still requires disassembly of all expanding elements or pins located above the bladders. In this case, too, the operation involved is substantially time-consuming and its outcome is unpredictable, as it is performed by the user of the shaft who is less experienced than the manufacturer of the same. Moreover, the machining of T or dovetail splines on the shaft surface is a considerably difficult and time-consuming task, which contributes to the high cost of manufacturing these shafts.
The mandrels according to the present invention fall into this second category. This invention is a development of the expansible mandrel described in the Applicant's U.S. Pat. No. 3,904,144.